While escalator handrail drive systems are known in the art, existing systems are frequently subject to mechanical failure and high maintenance due to constant use. This is particularly true with respect to escalator systems used in mass transit facilities. A popular escalator system for such mass transit facilities is the Westinghouse Moduline B-100 Escalator. The Metropolitan Atlanta Rapid Transit Authority ("MARTA"), for example, has over 120 Westinghouse modular escalators with over 360 handrail drive units. The Washington Metropolitan Area Transit Authority has some 500 of these same escalators with approximately 1600 handrail drive units. MARTA has reported that in excess of twenty percent of a typical mechanic's time is expended on problems associated with the handrail drive system, leading to the desire for a replacement system requiring less maintenance.
Maintenance problems with escalators in mass transit facilities, and with the handrail drive system in particular, are well known. For example, in 1980 the Jet Propulsion Laboratory and the California Institute of Technology published a report for the U.S. Department of Transportation entitled "Overview of Escalator Applications in Rail Transit" that described the high maintenance requirements for modular escalators and detailed the maintenance history for several mass transit systems. While modular escalators have a lower capital cost than conventional escalators, modular elevators are generally known for higher maintenance costs and lower availability.
Examples of the Westinghouse modular escalator system are found in U.S. Pat. No. 4,535,880 to Boltrek, U.S. Pat. No. 4,580,675 to Boltrek, and U.S. Pat. No. 4,589,539 to Boltrek, et al. One version of the handrail drive system is described in detail in U.S. Pat. No. 4,580,675, particularly FIG. 6 contained therein. The system uses a drive pulley, several auxiliary pulleys, a drive belt, several traction rollers, a take up pulley, and several pressure rollers. The pressure rollers are spring driven and bias the surface of the handrail against the traction rollers for point contact. See Column 5, lines 46-53.
The specific maintenance problems with the Westinghouse handrail drive system include heavy wear on the handrail and the urethane drive rollers. This wear is caused by the spring-loaded pressure or pinch rollers located under each drive roller that rotate against the face of the handrail. Further, the use of only point contact between the pressure rollers, the handrail, and the drive rollers does not provide enough surface contact on the handrail to create the necessary drive friction. Any unexpected load on the handrail, such as a person attempting to ride on it, can cause the handrail to slip and shut the system down.
What is needed is a handrail drive system that can provide increased force to handrails while decreasing the number of required parts and the amount of required maintenance. Such an improved system would preferably fit within existing escalator systems without substantial modifications.
The present invention is an improvement upon the Westinghouse system in that it replaces the existing six wheel roller drive system with a simplified system employing one drive wheel, one pair of pressure rollers, and one pair of guide rollers. The present invention has fewer moving parts and requires less maintenance, while exerting more drive force. This is due to the fact that both the pressure rollers and the drive wheel have a contact layer with a suitable hardness in order to squeeze the handrail between the pressure rollers and the drive wheel without causing damage. Further, the invention provides for significantly greater contact area between the drive wheel and the handrail, thereby permitting the transmission of greater drive force.
While other means of reducing handrail wear have been disclosed, such as U.S. Pat. No. 5,125,494 to Nurnberg, et al., employing the use of a slip ring to prevent the handrail from coming into contact with the drive belt, these disclosures require the use of additional moving parts, thereby leading to additional maintenance and an increased possibility of mechanical break down. The present invention, however, employs the use of an appropriate contact layer on the surface of the pressure rollers and drive wheel such that more force can be applied to the handrail with less wear than is possible with the known handrail drive systems.